2,3,3,3-tetrafluoropropene (CF3CF═CH2, HFO-1234yf) contains no chlorine and thus is useful as an alternative compound for chlorofluorocarbons to be used for e.g. refrigerants.
As a process for producing HFO-1234yf, a process may, for example, be mentioned wherein 1,1-dichloro-2,2,3,3,3-pentafluoropropane (CF3CF2CHCl2, HCFC-225ca) is subjected to a dehydrofluorination reaction to obtain 1,1-dichloro-2,3,3,3-tetrafluoropropene (CF3CF═CCl2, CFO-1214ya), and then, CFO-1214ya is reacted with hydrogen and reduced to obtain HFO-1234yf.
As a method of reducing CFO-1214ya to obtain HFO-1234yf, the following method (i) may, for example, be mentioned.
(i) A method for obtaining HFO-1234yf by reacting CFO-1214ya with hydrogen at a temperature of from 100 to 400° C. in the presence of a catalyst having palladium supported on alumina (Patent Document 1).
However, the method (i) has a problem such that together with HFO-1234yf, an excessively reduced product 3,3,3-trifluoropropene (CF3CH═CH2, HFO-1243zf) will be formed as a by-product which has a boiling point close to HFO-1234yf and thus cannot be separated therefrom by distillation.
On the other hand, as a method for carrying out a similar reduction reaction, the following method (ii) has been proposed.
(ii) a method of reacting RfCF═CX2 (wherein Rf is a C1-10 fluoroalkyl group, and X is chlorine, bromine or iodine) with hydrogen at a temperature of from 5 to 200° C. in the presence of a catalyst having palladium supported on active carbon, to obtain RfCF═CH2 (Patent Document 2).
However, also by the method (ii), together with the desired product RfCF═CH2, an excessively reduced product RfCH═CH2 may sometimes be formed as a by-product. For example, in a case where Rf is H(CF2)3—, there is a certain difference in boiling point between the desired product and the by-product, and they can be separated by distillation. However, in a case where Rf is CF3—, i.e. in a case where the desired product is HFO-1234yf, as mentioned above, the desired product and the by-product cannot be separated by distillation.